JP2000091408A - Electrostatic attraction apparatus and wafer processing apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sufficient attractive force between a wafer and electrode by making larger the potential difference between them than necessary for the breakdown of an oxide film which is stuck on the rear surface of the wafer. SOLUTION: An electrostatic attraction apparatus is formed by depositing a ceramics dielectric film 2 of 300 μm in its thickness on an aluminum electrode 1 through thermal spraying, and the electrode 1 is connected with a DC power supply 3 to apply to it an arbitrary voltage relative to a grounding potential 4. Also, in the state of loading a wafer 5 on the dielectric film 2, a grounding potential 6 is given to the wafer 5. Then, by applying a DC voltage to the electrode 1, the potential difference between the electrode 1 and wafer 5 is made larger than the necessary one for the breakdown of an oxide film stuck on the rear surface of the wafer 5. By accumulating charges on the dielectric film 2 and wafer 5, an electrostatic attractive force is generated between them to attract fixedly the wafer 5 to the electrode 1. As a result, there can be obtained a sufficient attractive force, even when whatever kind of electrically insulating film is stuck on the rear surface of the wafer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic attraction device and a wafer processing device using the same, and more particularly to an electrostatic attraction device used for fixing a wafer at the time of transferring or processing the wafer in a semiconductor manufacturing apparatus. 1. Field of the Invention The present invention relates to an electrostatic suction device suitable for use and holding, and a wafer processing apparatus using the same.

[0002]

2. Description of the Related Art A method of holding an object by using an electrostatic force is used particularly for transferring a wafer in a semiconductor manufacturing apparatus and fixing the wafer during each process. As a holding method for carrying or fixing the wafer, a mechanical holding method using a clamp or the like can be considered, but using an electrostatic force has many advantages in holding the semiconductor wafer. For example, since there is no mechanical contact with the processing surface of the wafer, there is no contamination of the wafer due to abrasion powder, etc., and since the wafer is fixed by suction on the entire back surface of the wafer, the warpage of the wafer can be corrected and the suction surface can be used in fine processing such as etching. Contact with the
The thermal conductivity is improved, and the temperature control of the wafer becomes easy.

[0003] As described above, electrostatic attraction has many advantages as a method of holding a wafer.
It is widely applied as a wafer processing electrode in devices such as D. However, in the electrostatic chucking device, since the electrostatic force of the electric charge stored in the dielectric film and the electric charge polarized near the back surface of the wafer generates an adsorbing force, the electric charge is stored in the dielectric film especially when the wafer is peeled off. There is a problem of responsiveness that the charge elimination time of the accumulated charge is long (that is, the residual adsorption force is large). If the response is poor, that is, if the charge elimination time is long, the waiting time until the next operation of transporting the wafer to the next processing chamber becomes long, which causes a problem that the processing capacity of the apparatus is reduced. Usually, a rod-shaped support (hereinafter referred to as a pusher) is moved vertically through a through hole provided in the electrode in order to pick up the wafer after processing from the electrode. If the wafer is forcibly peeled off, the wafer will be broken. This tendency becomes more serious as the diameter of the wafer increases with an increase in the degree of integration of elements, because the residual suction force increases.

A method for coping with such a problem caused by the residual suction force is disclosed, for example, in Japanese Patent Application Laid-Open No. 4-247639. In this disclosed example, as a method of quickly reducing the residual suction force generated in an electrostatic suction device having two electrodes connected to DC power supplies having different polarities, a voltage during which a wafer is being suctioned is first suctioned. There is disclosed a method of accelerating static elimination as a voltage having an absolute value lower than the voltage.

[0005] Japanese Patent Application Laid-Open No. 10-150100 is related to the present invention. This technology has a pair of electrodes having different polarities, a direct current voltage is applied between the electrodes, and an electrostatic chuck that electrostatically holds a sample on a dielectric film provided on the upper surface of the electrode is used as an electrode. The amount of electric charge stored in the adsorption portion of the dielectric film immediately before the stop of the supply of the DC voltage applied to the substrate is made substantially the same, and is eliminated by the balance of electric charges of different polarities, thereby reducing the residual adsorption force.

[0006]

SUMMARY OF THE INVENTION The electrostatic attraction device disclosed in Japanese Patent Application Laid-Open No. 4-247639 is capable of reliably adsorbing at the time of adsorption and shortening the time required at the time of detachment. A method is disclosed in which the voltage is made to have an absolute value larger than the voltage during adsorption.

However, in this method, when an electrically insulating oxide film or the like is provided on the back surface of the wafer, such as a wafer used in an actual process, a sufficient leak current cannot flow. Sufficient charge is not accumulated between the film surface and the back surface of the wafer, the adsorbing power is insufficient, and when a cooling gas is supplied to the back surface of the wafer to control the temperature of the wafer during processing, sufficient pressure does not rise, or the cooling gas This causes a problem such as an increased amount of leakage. as a result,
Poor wafer temperature control leads to, for example, deterioration of the etching shape, or the leaked cooling gas mixes with the processing gas to adversely affect the processing.

In addition, since some wafers have undergone various processes and have undergone deformation such as warping, the state of contact with the dielectric film has deteriorated, and sufficient leakage current must be supplied. Is not enough to accumulate electric charge even in cases such as when the adsorption force is reduced due to the inability to perform cleaning, or when an electrically insulating deposit is formed on the surface of the dielectric film of the electrostatic adsorption device. We may be underpowered, but we can't handle these cases. Furthermore, in a so-called bipolar electrostatic attraction device having two internal electrodes for applying a voltage, if the amount of positive and negative charges immediately before the applied voltage is turned off is different, a residual attraction force is easily generated,
As described above, if the wafer is warped or if it is not sufficiently absorbed by the electrically insulating film attached to the surface of the dielectric film, a difference occurs in the amount of positive and negative charges stored between the surface of the dielectric film and the back surface of the wafer, resulting in a residual. There is a problem that a suction force is easily generated.

A first object of the present invention is to provide an electrostatic attraction device having a large attraction force. A second object of the present invention is to provide an electrostatic chuck having good temperature controllability. Further, a third object of the present invention is to provide an electrostatic attraction device that does not generate residual attraction force.

[0010]

A first object of the present invention is to provide a dielectric film on an electrode made of a conductive material and to apply a potential difference between the electrode and a wafer disposed on the dielectric film. In an electrostatic attraction device that attracts and fixes a wafer by electrostatic force, this can be achieved by setting the potential difference between the electrode and the wafer to a potential difference larger than the potential difference required to cause dielectric breakdown of an oxide film on the back surface of the wafer.

A second object of the present invention is to provide a gas introducing means for introducing a heat conductive gas between the dielectric film and the back surface of the wafer, and to introduce the heat conductive gas by the gas introducing means. This can be achieved by giving a potential difference between the electrode and the wafer so as to cause dielectric breakdown of the oxide film.

A third object of the present invention is to form a dielectric film on two electrodes that are electrically insulated from each other so that the area of the actual suction portion on each electrode is the same, A voltage is applied to the electrodes and a potential difference is applied between the wafer and each electrode to attract and fix the wafer by electrostatic force. This is achieved by applying a voltage that is a potential difference. Further, by lowering the voltage immediately before the stop of the voltage application from the voltage during the suction, the residual suction force can be reduced more effectively.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
In this embodiment, a ceramic dielectric film 2 is formed by spraying 300 μm on an aluminum electrode 1, and the surface of the dielectric film is polished to a maximum height roughness of about 5 μm. . A DC power supply 3 is connected to the electrode 1, and a voltage can be arbitrarily applied to the ground 4 potentials. Therefore, when the wafer 6 is loaded on the dielectric film 2 and a ground 6 potential is applied to the wafer and a DC voltage is applied to the electrode 1, electric charges are stored in the dielectric film 2 and the wafer 5, and an electrostatic force is generated and attracted.・ Fixed. Here, the means for applying the ground 6 potential to the wafer 5 is not shown, but for example, a plasma is used in a dry etching apparatus. However, when used in an actual semiconductor manufacturing process, an oxide film of about 10,000 Å or less is usually formed on the back surface of the wafer, which is an object to be adsorbed, and the electrostatic force is small, that is, insufficient adsorption occurs. May be. The cause of the decrease in the attraction force when an oxide film is present on the back surface of the wafer will be described with reference to FIGS. FIG. 2 shows an equivalent circuit when the electrostatic chuck of the first embodiment sucks a silicon wafer and when a wafer with a back oxide film (8 inches) having a thickness of 10,000 angstroms is sucked and fixed. I have. 7 is a capacitance component of the dielectric film 2, 8 is a resistance component, 9 is a capacitance component of a gap between the dielectric film surface and the back surface of the wafer, 10 is a contact resistance of a gap between the dielectric film surface and the back surface of the wafer, and 11 is an oxidation of the back surface of the wafer. A capacitance component 12 of the film is a resistance component of the oxide film on the back surface of the wafer. The figure also shows an estimate of the approximate value of each component. The estimation is made by calculating the resistance of the dielectric film with an actual measurement value described later with reference to FIG. Regarding the gap between the surface of the dielectric film and the back surface of the wafer, the contact resistance is considered to be about the same as the resistance of the dielectric film in a vacuum where an electrostatic chuck is actually used. And the same resistance. The capacity was calculated as the capacity of a vacuum space having a maximum height roughness of 5 μm. Regarding the oxide film on the back surface of the wafer, the resistivity of silicon dioxide is set to 10 ¹⁵ Ωcm.
And the capacitance is 4
It is the value estimated as. On the other hand, the resistivity of a normal silicon wafer is about 10 Ωcm, and both the resistance component and the capacitance component can be ignored.

FIG. 3 shows the measurement results of the resistivity of the dielectric film of the electrostatic chuck of the first embodiment. In the present embodiment, ceramic is used for the dielectric film, and the resistance value changes as shown in the figure according to the applied voltage. FIG. 4 shows the measurement results of the applied voltage and the leak current of the back surface oxide film of the wafer with the back surface oxide film used in this example. As shown in the figure, it can be seen that the leak current hardly flows up to an applied voltage of 400 V, but increases sharply when the applied voltage exceeds 400 V. This is presumably because although the back oxide film has electrical insulation properties, dielectric breakdown occurs when a voltage higher than a certain voltage is applied. Consider a case where a voltage of -300 V is applied to the aluminum electrode in such a state. First, in the case of a silicon wafer, the voltage is divided according to the ratio between the resistance of the dielectric film and the contact resistance, and each capacitor is charged with electric charge. The electric charge that contributes to the attraction force is the electric charge charged between the gap between the dielectric film and the wafer, and in this case, it is 8.4 μC. However, in the case of a wafer with an oxide film, as shown in FIG. 4, the oxide film on the back surface of the wafer does not undergo dielectric breakdown, so that almost no leak current flows through the circuit, and the electric charge between the dielectric film and the back surface of the wafer is as shown in FIG. As shown, the voltage suddenly increases immediately after the application of the voltage, but gradually decreases, finally reaches 0 coulomb, and the attraction force disappears. In other words, the effect of adsorption and fixation can be expected only for a certain period of time immediately after the application of the voltage.

On the other hand, when -500 V is applied to the aluminum electrode, the resistance of the oxide film on the back surface of the wafer is sufficiently larger than the resistance of the dielectric film. In this case, a leak current flows due to dielectric breakdown of the oxide film, and the resistance is sufficiently lower than that of the dielectric film. In the case of the wafer with an oxide film of this embodiment, the value was about 1 × 10 ⁵ Ω.
Then, a leak current flows through the circuit, the voltage is divided also into the resistance and the contact resistance of the dielectric film, and each capacitor is charged. In this case, the state of the electric charge stored in the gap between the surface of the dielectric film and the back surface of the wafer is 14 μCoulomb as shown in FIG. 6, and even when the oxide film is provided on the back surface, the electric charge of 14 μCoulomb is similar to the case of the silicon wafer. It can be seen that it is stored, that is, the attraction force is generated.

As described above, in the electrostatic chucking apparatus configured to cause a leakage current by causing dielectric breakdown of the oxide film on the back surface of the wafer being processed, the chucking force is extremely reduced as compared with the silicon wafer. Nothing. In an actual semiconductor manufacturing process, a method of flowing a heat transfer gas to the back surface of a wafer is often used in order to improve the cooling efficiency of the wafer during processing. In such a case, the electrostatic suction device of the present invention is used. When used, since there is little variation in the attraction force due to the wafer, the reproducibility of the cooling state of the wafer becomes very good. For example, when applied to dry etching, etc., the production with a very high yield An apparatus can be provided.

FIG. 7 shows a second embodiment of the present invention. In this embodiment, a tungsten inner electrode 14 having the same area and concentrically arranged in a ceramic dielectric film 13 is provided.
And two ring electrodes 15 are buried, conductive wires 16 and 17 are connected to the respective electrodes, and DC power supplies 18 and 19 are connected to apply DC voltages having different polarities to the respective electrodes. As in the first embodiment, the surface of the dielectric film is polished to a maximum height roughness of 5 μm, and the thickness of the dielectric film on the internal electrodes is 300 μm. Therefore, when a DC voltage is applied to each electrode in a state where the wafer 5 is mounted on the dielectric film, electric charges are stored in the dielectric film and the wafer, and an electrostatic force is generated to be attracted and fixed. FIG. 8 shows an equivalent circuit in the case where a silicon wafer is sucked based on the same concept as in the first embodiment and the case where a wafer with a back surface oxide film of 10,000 Å is sucked. This embodiment has a configuration in which two equivalent circuits of the first embodiment are connected in series. The numbers in the figure are
Reference numerals 54 and 55 denote the resistance component and the capacitance of the dielectric film on the inner electrode 14, respectively.
Above are the resistance component and capacitance. 56, 57 are the contact resistance and the gap capacitance between the surface of the dielectric film on the inner electrode and the back of the wafer;
Reference numerals 0 and 61 denote contact resistance and capacitance between the surface of the dielectric film on the ring electrode 14 and the back surface of the wafer. 62 and 63 are the resistance components and capacitance of the oxide film on the back surface of the wafer on the inner electrode 14, and 64 and 65 are the resistance components and capacitance of the oxide film on the ring electrode 14. In the figure, the values of each resistance component and capacitance component obtained based on the same concept as described in the first embodiment are described. In this state, +300 V is applied to the inner electrode 14 and −300 V is applied to the ring electrode 15.
Is applied. In the case of a silicon wafer, the resistance component and the capacitance component of the oxide film are negligible, so that the voltage is divided in proportion to the magnitude of each resistance component, and each capacitance component is charged. The electric charge stored in the gap between the dielectric film surface and the wafer back surface, which contributes to the attraction force, is 8.4
μ coulomb. FIG. 9 shows a state in which the charge increases. On the other hand, in the case of a wafer with an oxide film, the applied DC voltage causes dielectric breakdown of the oxide film on the back surface of the wafer so that a leak current cannot flow. , But gradually decreases and finally reaches 0 coulomb, and the attraction force disappears. In other words, the effect of adsorption and fixation can be expected only for a certain period of time immediately after the application of the voltage. On the other hand, when +500 V and -500 V are applied to the inner electrode 14 and the ring electrode 15, respectively, almost all of the dielectric material immediately after the voltage application is applied because the resistance of the oxide film on the back surface of the wafer is sufficiently larger than the resistance of the dielectric film. Since the voltage is applied to the body film, the oxide film is broken down and the resistance is sufficiently reduced as compared with the dielectric film. In the case of the wafer with an oxide film of this embodiment, the value was about 1 × 10 ⁵ Ω. Then, a leak current flows through the circuit, the voltage is divided also into the resistance and the contact resistance of the dielectric film, and each capacitor is charged with electric charge. In this case, the state of the electric charge stored in the gap between the dielectric film surface and the back surface of the wafer is as shown in FIG. 10, and even when the back surface has an oxide film, the electric charge of 14 μC is stored as in the case of the silicon wafer. That is, it can be seen that the suction force is generated.

As described above, in the electrostatic chucking device configured to cause a leakage current by causing dielectric breakdown of the oxide film on the back surface of the wafer being processed, the chucking force is extremely reduced as compared with the silicon wafer. Nothing. In an actual semiconductor manufacturing process, a method of flowing a heat transfer gas to the back surface of a wafer is often used in order to improve the cooling efficiency of the wafer during processing. In such a case, the electrostatic suction device of the present invention is used. When used, since there is little variation in the attraction force due to the wafer, the reproducibility of the cooling state of the wafer becomes very good. For example, when applied to dry etching, etc., the production with a very high yield An apparatus can be provided.

In this embodiment, the inner electrode 14, the ring electrode 1
Although the same voltage having an absolute value with a different polarity was applied to each of the electrodes 5, the voltage need not always be applied. Only one of them may be applied, or a voltage having a different absolute value may be applied to each internal electrode. The important point is that the oxide film on the back surface of the wafer is broken down by applying a voltage and a leak current flows. To this end, a partial voltage of a withstand voltage or more is applied to the oxide film on the back surface of the wafer. It is. Therefore,
In the case of a combination different from the dielectric film and the wafer back surface oxide film described in the first and second embodiments, the required applied voltage is required because the partial pressure applied to each resistance component and the withstand voltage of the back surface oxide film are different. Will vary, but should be appropriately determined according to the implementation conditions.

FIG. 11 shows an example in which the electrostatic chuck according to the second embodiment of the present invention is applied to a magnetic field microwave plasma processing apparatus. The configuration and operation of the device will be briefly described. A quartz tube 21 is installed in an atmospheric space 20, and a wafer 5 is fixed to a base 24 using an electrostatic suction device 23 in a vacuum processing chamber 22 formed by the quartz tube 21. Subsequently, the processing gas 25 is introduced into the vacuum processing chamber 22. The processing gas is generated by the microwave generator 26 and is brought into the plasma 32 state by the interaction of the microwave 28 introduced through the waveguide 27 and the coils 30 and 31 attached around the microwave resonance box 29. Has become. The processing (here, etching processing) is performed by exposing the wafer 5 to the plasma 32. The high-frequency power supply 33 controls the etching state by controlling the incidence of ions, in particular. To explain other numbers in the drawing, reference numeral 34 denotes a DC power supply for the electrostatic chucking device, 3
Reference numerals 5 and 39 are switches for controlling on / off of the DC power supply. 36 is a coil for protecting the DC power supply from high frequencies, and 37 is a blocking capacitor. Reference numeral 38 denotes an exhaust of an excess processing gas and a reaction product, and is connected to a vacuum pump (not shown).

The electrostatic attraction device 3 will be described in detail with reference to FIG. However, the dimensional ratios of the components in the drawings are different from the actual dimensional ratios for easy understanding.

The basic structure of this device is an aluminum block 40
A dielectric film 43, which is a 1 mm-thick alumina sintered body in which two electrodes, ie, a ring electrode 41 and an inner electrode 42 are concentrically embedded, is fixed by an adhesive 44 thereon. I have. The two electrodes 41 and 42 have a thickness of about 50 to 100 microns and are made of tungsten. The dielectric film thickness on each of the electrodes 41 and 42 is
The surface roughness is 300 μm, and the surface roughness is 3 μm. On the front surface 45 of the dielectric film, a cooling gas introduced from a cooling gas inlet 46 through an external pipe (not shown) to promote cooling of the wafer being processed is applied to the entire back surface of the wafer. Gas groove 47 for efficient distribution is 100 depth
Engraved in microns, as shown. The gas groove pattern is set so that the temperature distribution of the wafer being processed becomes a desired value. The application of the DC voltage to these two electrodes is performed by using the conductor 4 completely sealed with the insulating resin 48.
9 is performed. The conductor 49 and each electrode are brazed 50. In this embodiment, the inner electrode 42 is connected to the positive potential of the DC power supply 51 or the ground 6 by a switch 39, and the ring electrode 41 is connected to the negative potential of the DC power supply 34 by a switch 35. 6 is connected. Then, with the wafer loaded on the surface 45 of the dielectric film 43, the ring electrode 4
When a negative voltage is applied to 1 and a positive voltage is applied to the inner electrode 42, a potential difference is generated between the wafer and each electrode, so that the wafer can be electrostatically attracted and fixed. If the inner electrode 42 is grounded 6, the charge stored between the wafer and each electrode can be eliminated. 5
Reference numeral 2 denotes a pusher used for transferring a wafer after the processing, and is insulated by an insulating cylinder 53.

FIG. 13 illustrates a method of applying a voltage to the electrostatic chuck according to the present embodiment. As described above, the back surface of the processing wafer is provided with oxide films of various thicknesses. The oxide film thickness of the back surface of the wafer used in the plasma processing of this embodiment is 10,000 Å at the maximum, and FIG. From this, it can be seen that the oxide film undergoes dielectric breakdown at a voltage having an absolute value of 400 V or more, and in this embodiment, +500 V is applied to the ring electrode 41 and -500 V is applied to the inner electrode 42 immediately after the start of the voltage application to sufficiently attract and fix. During this time, pressure control is performed by introducing a cooling gas to the back surface of the wafer via the cooling gas introduction port. However, since a sufficient suction force is generated, the rise time of the pressure of the cooling gas can be short. After the pressure reaches a certain level, it becomes possible to process the wafer by applying a plasma discharge or RF bias. At this time, for example, the voltage of the electrostatic chuck is +300 V to the ring electrode 41 and −300 V to the inner electrode 42. Make it as low as 300V. Once the oxide film on the back surface of the wafer is broken down, the resistance decreases at that portion and current easily flows, so that the attraction force does not extremely decrease. In addition, when the wafer is peeled off after the processing, the wafer can be more smoothly peeled off because the wafer is not attracted with an excessive suction force during the processing.

In the processing apparatus configured as described above, even if any wafer having a different backside oxide film thickness is processed, the rise time of the pressure of the cooling gas introduced to the backside of the wafer can be reduced, and the processing after the processing is completed. Since the time for reducing the residual adsorption force can be shortened, the processing capacity of the apparatus is not impaired.

FIG. 14 shows a fourth embodiment of the present invention. In this embodiment, when the pressure of the cooling gas decreases during the plasma processing, the applied voltage during the adsorption is applied to the ring electrode 41.
-800 V and -800 V applied to the inner electrode 42 for 3 seconds, respectively. Such an operation is required when the wafer has been warped due to various processes or when the insulating material is deposited on the surface of the dielectric film as the number of processed electrostatic chucks increases. Is the case. In other words, what was initially sufficient to cause dielectric leakage of the oxide film on the backside of the wafer and allow leakage current to flow, but could not be sufficiently broken down due to insufficient adsorption due to wafer warpage, This is the case where the applied voltage is divided at the insulator portion, so that the applied voltage is not sufficient to cause dielectric breakdown of the oxide film. Even in such a case, a sufficient suction force can be secured by performing the operation as in the present embodiment. Therefore, by providing the electrostatic suction device of the present embodiment, a highly reliable processing device can be provided.

According to the operation of this embodiment, the effect of reducing the residual suction force can be expected. In other words, in a so-called bipolar electrostatic chuck having two electrodes inside, the area of the dielectric film on each electrode is the same, and when the amount of positive and negative charges immediately before stopping the applied voltage is the same, the residual attraction force is reduced. Although generation is suppressed, if the adsorption on the two electrodes is insufficient for the above-described reason, the amount of positive and negative charges varies, and a residual adsorption force is easily generated. However, by performing sufficient adsorption by the operation of the present embodiment, the state of adsorption on the two electrodes is the same, that is, by making the amount of positive and negative charges the same, it is possible to suppress the generation of residual adsorption force. Therefore, since the generation of the residual suction force can be suppressed by the electrostatic suction device of the present invention, a wafer processing device equipped with the present device can provide a highly reliable device without a reduction in the processing capability of the electrostatic suction device. be able to.

In the embodiments of the present invention, an oxide film has been described as an insulating film on the back surface of a wafer. However, this is not always necessary. For example, a nitride film or a polymer film may be used in the same manner. Can expect the same effect.

[0028]

As described above, according to the present invention, even if an electrical insulating film of any kind is adhered to the back surface of the wafer, the dielectric breakdown is caused and a leak current flows to attract and fix the wafer. An electrostatic attraction device capable of obtaining an attraction force can be provided. In addition, when applied to a semiconductor manufacturing apparatus or the like, the rise time of the pressure of the cooling gas introduced into the back surface of the wafer can be shortened, and the reduction time of the residual adsorption force after the processing can be shortened. An electrostatic attraction device that does not impair the processing capability of the device can be provided. Further, even when a wafer warped after each process is suctioned, or when an electrically insulating film is attached to the dielectric film surface by stacking the number of processed wafers, the wafer can be sufficiently suctioned. Therefore, a highly reliable processing device can be provided. Also, in a so-called bipolar electrostatic attraction device having two internal electrodes, the generation of residual attraction force is suppressed, so that a wafer processing apparatus equipped with the present device can prevent a reduction in processing capacity due to the generation of residual attraction force. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the electrostatic suction device of the present invention.

2 is an equivalent circuit diagram when a silicon wafer and a wafer with a backside oxide film are electrostatically attracted in the apparatus of FIG. 1;

FIG. 3 is a diagram showing a relationship between an applied voltage of a dielectric film and a resistivity in the device of FIG.

FIG. 4 is a diagram showing a relationship between an applied voltage of a back oxide film and a leak current of the wafer with a back oxide film used in FIG. 2;

FIG. 5 is a diagram showing a change over time of a charge between the front surface of the dielectric film and the back surface of the wafer in the apparatus of FIG. 1;

FIG. 6 is a diagram showing a change over time of a charge between the front surface of the dielectric film and the back surface of the wafer at different applied voltages in the apparatus of FIG. 1;

FIG. 7 is a sectional view showing a second embodiment of the electrostatic suction device of the present invention.

8 is an equivalent circuit diagram when a silicon wafer and a wafer with a backside oxide film are electrostatically attracted in the apparatus of FIG. 7;

9 is a diagram showing a change over time of a charge between the front surface of the dielectric film and the back surface of the wafer in the apparatus of FIG. 7;

FIG. 10 is a diagram showing a change over time of a charge between the front surface of the dielectric film and the back surface of the wafer at different applied voltages in the apparatus of FIG. 7;

FIG. 11 is a sectional view showing a wafer processing apparatus using the electrostatic suction device of FIG. 7;

FIG. 12 is a perspective view of an electrostatic suction device of the device of FIG. 11;

FIG. 13 is a time chart of a voltage applied to the device of FIG. 12;

FIG. 14 is a time chart showing another example of the voltage applied to the device of FIG. 12;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode, 2 ... Dielectric film, 3 ... DC power supply, 4 ... Ground, 5
... wafer, 6 ... ground, 7 ... dielectric film capacitance component, 8 ... dielectric film resistance component, 9 ... gap capacitance component, 10 ... contact resistance, 11 ... backside oxide film capacitance component, 12 ... backside oxidation Resistance component of film, 13: dielectric film, 14: internal electrode, 15
... internal electrode, 16 ... lead, 17 ... lead, 18 ... DC power supply, 19 ... DC power supply, 20 ... atmosphere space, 21 ... quartz tube,
22: vacuum processing device, 23: electrostatic adsorption device, 24: base, 25: processing gas, 26: microwave generator, 27
... waveguide, 28 ... microwave, 29 ... microwave resonance box, 30 ... coil, 31 ... coil, 32 ... plasma, 3
3: High frequency power supply, 34: DC power supply, 35: Switch, 3
6: coil, 37: blocking capacitor, 38: exhaust, 39: switch, 40: aluminum block, 41: ring electrode, 42: inner electrode, 43: dielectric film, 44: adhesive, 45: surface of the dielectric film , 46 ... gas inlet, 47 ...
Gas groove, 48 ... resin, 49 ... lead wire, 50 ... brazing, 5
1 DC power supply 52 Pusher 53 Insulated cylinder 54
55: resistance component of the dielectric film on the inner electrode; 55: capacitance of the dielectric film on the inner electrode; 56: contact resistance between the dielectric film on the inner electrode and the back surface of the wafer; 57: gap capacitance on the inner electrode; Resistance component of the dielectric film on the ring electrode, 59: capacitance of the dielectric film on the ring electrode, 60: contact resistance between the dielectric film on the ring electrode and the back surface of the wafer, 61: gap capacitance on the ring electrode, 62 ... Resistance component of oxide film on back surface of wafer on inner electrode, 6
3 ... Capacity of the wafer backside oxide film on the internal electrode, 64 ... Resistance component of the wafer backside oxide film on the ring electrode, 65 ... Capacity of the wafer backside oxide film on the ring electrode.

Continuing on the front page (72) Inventor Takeshi Yoshioka 794, Higashi-Toyoi, Oji, Kudamatsu-shi, Yamaguchi Prefecture Inside the Kasado Plant of Hitachi, Ltd. Inside the Kasado Plant (72) Inventor Saburo Kanai 794, Higashi-Toyoi, Kazamatsu-shi, Yamaguchi Prefecture F-term in the Kasado Plant, Hitachi, Ltd. 5F031 FF03

Claims (8)

[Claims] An electrostatic capacitor for providing a dielectric film on an electrode made of a conductive material, applying a potential difference between the electrode and a wafer disposed on the dielectric film, and attracting and fixing the wafer by electrostatic force. In the suction device, the potential difference is a potential difference that is larger than a potential difference required to cause dielectric breakdown of an oxide film on the back surface of the wafer. 2. An electrostatic device comprising: a dielectric film provided on an electrode made of a conductive material; a potential difference between the electrode and a wafer disposed on the dielectric film; An electrostatic attraction device, wherein the potential difference is increased at least once during the attraction of the wafer to cause dielectric breakdown of an oxide film on the back surface of the wafer. 3. The electrostatic attraction device according to claim 1, further comprising one electrode, wherein the potential of said wafer is given by plasma for processing said wafer. 4. An electrostatic chuck according to claim 1, wherein said two electrodes are insulated from each other, and a potential difference is applied between said two electrodes to attract and fix said wafer. Characteristic electrostatic suction device. 5. An electrostatic chuck according to claim 1, further comprising a gas introducing means for introducing a heat-conducting gas between said dielectric film and the back surface of said wafer, said gas introducing means comprising: An electrostatic attraction device for applying a potential difference between the electrode and the wafer in order to break down an oxide film on the back surface of the wafer when introducing a heat conductive gas. 6. The electrostatic chuck according to claim 5, wherein
An electrostatic suction device, wherein a potential difference applied between the electrode and the wafer after the pressure of the heat-conducting gas reaches a reference value is reduced. 7. On two electrodes electrically insulated from each other,
A dielectric film is formed so that the area of the actual suction portion on each electrode is the same, a voltage is applied to these two electrodes, a potential difference is applied between the wafer and each electrode, and the wafer is suction-fixed by electrostatic force. An electrostatic chucking device in which a voltage that is a potential difference required to cause dielectric breakdown of a back surface oxide film of a wafer is applied at least once during the chucking. 8. A wafer processing apparatus comprising the electrostatic attraction device according to claim 1.